Digger Cake Help

My soon to be three year old has asked for a digger cake (as in 'Scoop' of Bob the Builder) for his birthday party. I've searched high and low for some step by step instructions or a video tutorial of the best way to make a cake like this but haven't been successful.

Just wondering whether any of you lovely members have made a cake like this and if you have, whether you have some easy instructions for me.

I've made many childrens birthday cakes but they've always been a bit more simple than this. I know it's probably just a matter of cutting cakes into rectangles, squares, etc but just don't know where to start.